A number of chlorine-containing halocarbons are considered to be detrimental toward the Earth's ozone layer. There is a world-wide effort to develop materials having lower ozone depletion potentials that can serve as effective replacements. For example, the hydrofluorocarbon, 1,1,1,2-tetrafluoroethane (HFC-134a) is being used as a replacement for dichlorodifluoromethane (CFC-12) in refrigeration systems. There is a need for manufacturing processes that provide fluorocarbons that contain less chlorine or no chlorine.
Numerous processes have been developed for changing the fluorine content of halogenated hydrocarbons. Various catalysts have been proposed for use in facilitating processes such as fluorination. See, e.g., L. E. Manzer et al., Adv. Catal. (39) pp. 329-350 (1993).
Chromia catalysts, which include crystalline Cr.sub.2 O.sub.3, amorphous phases and mixtures, have been widely used for halogenated hydrocarbon processing. Typically, the activity of these chromia catalysts decrease with time during their use in hydrofluorination processes. WO 94/06558 discloses that a major cause of this deactivation is the conversion of chromia to chromium trifluoride. CrF.sub.3 has been reported to form rhombohedral crystals (see e.g., Ullman's Encyclopedia of Industrial Chemistry, Fifth Ed., Vol. A7, p. 83). There is an ongoing interest in developing efficient catalysts for changing the fluorine content of halogenated hydrocarbons.